Rectus capitis lateralis muscle revisited: a histological study using human fetuses.

Area of Science:

• Anatomy
• Embryology
• Histology

Background:

• The rectus capitis lateralis muscle (RCLM) is situated between ventral and dorsal muscle groups.
• Its precise topographical anatomy and nerve relationships remain unclear.

Purpose of the Study:

• To investigate the detailed anatomical and topographical characteristics of the RCLM in fetal development.
• To clarify the relationship between the RCLM and surrounding structures, including nerves and bone, during fetal growth.

Main Methods:

• Histological analysis of fetal head sections from midterm (9-18 weeks) and near-term (26-40 weeks) fetuses.
• Observation of the RCLM's position, attachments, and relationship with adjacent bony structures and nerves.

Main Results:

• The RCLM attaches to the inferolateral aspect of the occipital bone, supporting the internal jugular vein.
• The muscle's upper insertion on the jugular process influences its ossification and contributes to occipital and temporal bone fusion.
• The ventral ramus of the first cervical nerve runs between the RCLM and rectus capitis anterior, without passing near the obliquus capitis superior.

Conclusions:

• The RCLM's position suggests a correspondence with the scalenus posterior muscle in cervical musculature.
• The study elucidates the RCLM's role in fetal neck development, venous support, and bone formation.